title: Age-related changes of periodontal ligament surface areas during force application.
abstract: OBJECTIVE
  To investigate the age-dependent morphology of the periodontal ligament (PDL) tissue and changes in its surface area (SA) during force application provided with a standardized orthodontic setup for a period of 12 weeks in young and adult rats.
  
  
  METHODS
  Two groups of 30 rats, age 6 weeks and 9 to 12 months, were used. Orthodontic appliances were placed to move the maxillary molars mesially with the contralateral sides used as controls. At 1, 2, 4, 8, and 12 weeks, groups of animals were killed. The PDL SA and the PDL SA ratio between pressure and tension regions were determined.
  
  
  RESULTS
  An age-related decrease in the PDL SA was noted at control sides. Significant changes during the experimental period occurred only at experimental sides: The PDL SA was smaller at pressure than at tension regions only at week 1 in young rats; in adult rats, the difference between the two regions was significant at week 8. These changes were confirmed by the morphologic disorganization of the PDL and alterations in the PDL SA ratio.
  
  
  CONCLUSIONS
  During force application, the PDL at the pressure regions became disorganized and subsequently was reorganized, as is shown by the histologic changes and SA of the PDL over time. This process occurred earlier and was more prominent in young rats; it occurred later and was more prolonged in adult animals.
authors.affiliation: Department of Orthodontics, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands. y.ren@dmo.umcg.nl
authors.forename: Yijin
authors.initials: Y
authors.lastname: Ren
authors.forename: Jaap C
authors.initials: JC
authors.lastname: Maltha
authors.forename: Lets
authors.initials: L
authors.lastname: Stokroos
authors.forename: Robert S B
authors.initials: RS
authors.lastname: Liem
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Kuijpers-Jagtman
mesh_terms: D000375:Aging / Q000473:pathology*; D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D003094:Collagen; D008297:Male; D008963:Molar / Q000473:pathology; D009967:Orthodontic Appliances; D010006:Osteoblasts / Q000473:pathology; D010010:Osteoclasts / Q000473:pathology; D010513:Periodontal Ligament / Q000473:pathology*; D011312:Pressure; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation
chemical_list: D003094:Collagen